Regarding the prism assembly of precision light beam scanner as a finite element model,the optical-mechanical-thermal integrating analysis was done. In terms of structure statics,the structure design and intensity of the prism assemble was verified and checked,and the surface deformation analysis of the prism was correspondingly provided under steady-state mechanical loading;Through the mode analysis,the dynamic characteristic of the device and the vibration amplitude change of the prism surface was obtained;then the hot elasticity distortion of the prism was analyzed and the estimation of optics performance of the prism was given. The analysis results show: the maximal distortion of the prism assembly was 10 nm magnitude and the maximal stress was 0.403 MPa,which has much tolerance to the admissible stress of material and the precision requirement of structure;The natural frequency of the front prism assembly and the back one both were greater than 550 Hz,which indicated the dynamic performance of the device very well. Through comparing thermal-structure coupling analysis with mechanical loading analysis,the influence of heat effect on the prism surface deformations was proved far greater than the influence of mechanical loading,so the strict temperature-controlled measure must be taken when the device is used.